Wave 1:
Hati, 700k, 2 turns, random 3x 2500-3000 damage
Storm Katze, 400k, 2 turns, all heal for 25%
Ratatoskr, 600k, 1 turn, all combo+ (240 seconds)
Kill priority: Top, bottom, middle
Nothing special here. Middle should just be ignored. Gaia owners might want to kill bottom first since Gaia can negate top Overdrive.
Wave 2:
Urcaguary, 5m, 4 turns
Normal: Random 1x 4000 damage + damage cut (-50%?)(5 hits?)
Rage: Random 3x 4000 damage + heal 50k
Gauge behavior: Rage at 80%, Stun at 25%?, does not free.
Trigger 1: First action: clear all debuffs + Def Up (+20%?)(doesn't expire)
Trigger 2: Turn 20: All 13000 damage
MAKE SURE NOT TO DEBUFF ON TURN 1.
This thing is quite tanky, but anyone who can meet the damage requirements of Wave3 shouldn't have issues. Considering his Def buff, 0.3m/t or so should dispatch this guy, and the damage requirement for Wave3 is 1.25m/t.
Still, he is tanky and he can be somewhat painful. Weaker players might need to Full Burst at the start. If you're still having issues, you might not be strong enough for Wave3 anyway but... try bringing Dispel maybe?
Stronger players can unleash skills on turn2 and then just auto-combat her down. For the record, this tactic takes my ~45k Atk Wind team about 9-10 turns to kill with -50% Def, which perfectly sets up Hraes to be available for Wave3.
Again, Gaia can just negate Overdrives entirely. Because why not make all Thunder stuff single target?